Magnetic adjusting means for magnetic translating device



J. A. SAWYER May 25, 1965 MAGNETIC ADJUSTING MEANS FOR MAGNETICTRANSLATING DEVICE Filed Jan. 23, 1962 INVENTOR. (73,? d .27. 6'0! e2 5?W "PM nrr'rr United States Patent 3,185,779 MAGNETIC ADJUSTING MEANS FORMAGNETIC TRANSLATING DEVICE v Joseph A. Sawyer, Camden, Maine, assignorto Tibbetts Industries, Inc., Camden, Maine, a corporation of MaineFiled Jan. 23, 1962, Ser. No. 168,160 15 Claims. (Cl. 179-114) Thisinvention is related to magnetic translating devices, and is especiallyconcerned with means to provide'a Vernier adjustment of the magneticcharacteristics of such translating device.

It is an object of this invention to provide a means enabling fineadjustment of the magnetic characteristics of a magnetic translatingdevice after previous coarse adjustments and assembly in a substantiallycomplete casing making further coarse adjustments difficult if notimpossible.

Another object of the invention is to provide a magnetic adjustmentwhich can be adjusted from the exterior of the case after the componentsof a magnetic translating device are assembled within the case of thedevice.

A further object of the invention is to provide a simple, rugged, easilyadjusted means to vary the magnetic characteristics of a magnetictranslating device from the exterior of a casing especially anadjustment means which can then be fixed in final position.

For the purpose of illustration a typical embodiment of the invention isshown in the accompanying drawings in which- FIG. 1 is a plan view of atranslating device embodying the invention;

FIG. 2 is a section on line 22 of FIG. 1;

FIG. 3 is a side view of the magnetic adjusting means; and

FIG. 4 is an end view of the adjusting means.

The particular translating device chosen for the purpose of illustrationis described and claimed in copending application Ser. No. 168,183 filedJanuary 23, 1962. It comprises a casing 1 of magnetic material, a foldedarmature 2 having one end 3 fixed in a recess in plate 5 as by spotwelding, the other end 6 being free to vibrate between the upper andlower magnets 7 and 8 provided with pole pieces 9 having tapered polefaces, the pole pieces being spaced apart by shim spacers 11. Whenutilized as a transducer the translating device may include a coil 12through which the armature passes. A drive pin 13 has its lower endfastened to the free end of the armature and passes through a hole 15 inthe armature to a driven or driving element such as the diaphragm of amicrophone or receiver. Damping means 16 is seated in a recess in plate5 and attached to the plate and armature as by epoxy adhesive. Themagnets 7 and 8, extending laterally of the plane of the armatures freeend on opposite sides thereof, may comprise any suitable permanentmagnetic material having suiiiciently high coercive field and availablemagnetic energy. The magnets are magnetized approximately perpendicularto the plane of the free end of the armature, and have opposite polesfacing each other across the gap in which the free armature endvibrates.

In the illustration a preferred embodiment of the aforesaid adjustingmeans comprises a circular disk 18 mounted in an opening in the end ofthe casing 1, the disk having a protuberance 19 projecting into thevicinity of means 79 creating a magnetic field in the translatingdevice. Both the disk 18 and the protuberance 19 are made of magneticmaterial such as a nickel-iron alloy. The protuberance 19 may beintegral with the disk or it may be attached to the disk in any suitableway. As

3,185,779 Patented May 25, 1965 shown in FIG. 4 the protuberance isoffset from the axis of the disk. Thus, by rotating the disk in thecasing opening by appropriate means exterior of the casing, theprotuberance may be moved relatively to the pole pieces to be more orless opposite a pole piece, thus shorting some of the field collected bythat pole piece to the casing. When the protuberance is parrallel to theplane of the armature it affects only the adjacent pole piece to anysubstantial extent. v When it is perpendicular to the plane of thearmature it shorts both pole pieces the same amount. At any intermediateposition it shorts flux between the casing and one pole piece more thanit shorts flux between the casing and the other pole piece. After theshorting means is adjusted to the desired position, as indicated byappropriate testing equipment, the disk 18 may be afiixed to the casingby any suitable means, as for example by an adhesive such as epoxy orthe like.

The invention is useful in other forms of translating devices, utilizingone or more magnets transverse or lengthwise of the armature. It mayreadily take other forms such as a rectilinearly sliding or screwadjusted mass movable nearer one or the other of the pole pieces, andmay occupy positions other than shown such as adjacent the shims, aswill be obvious to the artisan. However, the invention is to be limitedonly by the scope of the appended claims.

I claim:

1. A magnetic translating device comprising a casing of magneticmaterial, means within the casing defining opposed surfaces with a gaptherebetween, means for creating magnetic flux between the two surfaces,and means mounted on said casing adjacent said gap to short a part ofsaid flux from either surface to said casing.

2. A device according to claim 1 wherein said last means is adjustablefrom outside the casing.

3. A device according to claim 1 wherein said last means comprises asupport engaging the casing and a protuberance projecting toward saidgap.

4. A device according to claim 3 wherein the support is a disk and theprotuberance projects from one side of the disk ofi center.

5. A magnetic translating device comprising a casing of magneticmaterial, within the casing opposed surfaces with a gap therebetween,means for creating magnetic flux between the two surfaces, and meansmounted on said casing adjacent said gap to short a part of said flux tosaid casing, said means including a mass of soft magnetic materialmovable transversely of said gap.

6. A magnetic translating device according to claim 5 wherein said meanscomprises a rotor and said mass comprises a protuberance eccentricallydisposed on the rotor.

7. A magnetic translating device according to claim 5 furthercharacterized by means outside the casing for moving said massas'aforesaid.

8. A magnetic translating device comprising a casing of magneticmaterial, within the casing opposed poles with a gap therebetween. meansfor creating magnetic flux between the two poles, an armature having aportion vibratable lengthwise of said gap, and means mounted on saidcasing adjacent said gap to short a part of said flux from either ofsaid poles, said means including a mass of soft magnetic materialmovable lengthwise of said gap.

9. A magnetic translating device according to claim 8 wherein said meanscomprises a rotor and said mass comprises a protuberance eccentricallydisposed on the rotor.

10. A magnetic translating device according to claim 8 furthercharacterized by means outside the casing for moving said mass asaforesaid.

11. In a magnetic translating device of the balanced armature type inwhich one end of an armature is vibratable in a gap between spaced polefaces which are of opposite magnetic polarities relative to the otherend of the armature which is at a neutral magnetic potential, and havinga permeable casing which is also magnetically neutral, the improvementcomprising a protuberance of magnetic material mounted on said casingand adjustably positionable adjacent said gap for differentiallyshunting flux from said pole faces to said casing and out of the gap soas to provide a control over the residual flux passing through thearmature.

12. In a magnetic translating device of the balanced armature type inwhich one end of an armature is vibratable in a gap between spaced polefaces which are of opposite magnetic polarities relative to the otherend of the armature which is at a neutral magnetic potential, and havinga permeable casing which is also magnetically neutral, the improvementcomprising a disk of permeable material rotatably mounted on said casingadjacent the gap and a permeable protuberance eccentrically mounted onsaid disk and projecting toward the gap for differentially shunting fluxfrom said pole faces to the casing and out of the gap to an extentdependent upon the angular position of said disk thereby to provide acontrol over the residual flux passing through the armature.

13. Apparatus according to claim 12 in which said disk is rotatable fromoutside of said casing.

14. A magnetic translating device comprising a casing of magneticmaterial; a pair of magnet means for providing a pair of spaced polefaces of opposite magnetic polarities within said casing, said casingbeing at a neutral magnetic polarity; an armature one end of which isattached to said casing and the other end of which is vibratable in thegap between the pole faces; a coil around said armature for sensingchanges in the magnetic flux passing through said armature; and aprotuberance of magnetic material mounted on said casing adjacent saidgap and extending adjustably toward said gap for ditiererntiallyshunting flux from said pole faces to said casing and out of said gapthereby to provide a control over the residual flux passing through saidarmature.

15. A magnetic translating device according to claim 14 furthercomprising a disk of magnetic material rotatably mounted in an aperturein said casing, said protuberance being eccentrically mounted on saiddisk.

References Qited by the Examiner UNITED STATES PATENTS 2,493,388 1/50Candy 336-133 2,860,313 11/58 Israel 336-133 3,047,846 7/62 Koscheleff336-133 ROBERT H. ROSE, Primary Examiner.

E. JAMES SAX, Examiner.

1. A MAGNETIC TRANSLATING DEVICE COMPRISING A CASING OF MAGNETICMATERIAL, MEANS WITHING THE CASING DEFINING OPPOSED SURFACES WITH A GAPTHEREBETWEEN, MEANS FOR CREATING MAGNETIC FLUX BETWEEN THE TWO SURFACES,AND MEANS MOUNTED ON SAID CASING ADJACENT SAID GAP TO SHORT A PART OFSAID FLUX FROM EITHER SURFACE TO SAID CASING.